This invention relates to devices useful to augment bone deficiencies encountered during joint arthroplasty procedures.
Joint arthroplasty is a well known surgical procedure by which a diseased and/or natural joint is replaced by a prosthetic joint. Joint arthroplasty is commonly performed for knees, hips, elbows, and other joints. In some instances, due to disease or trauma, insufficient healthy boney mass exists at the distal end of a bone to which a joint prosthesis is to be secured. In arthroplasty procedures, it is often necessary to remove a portion of bone (such as a portion of the femur) to ensure sufficient anchoring and a proper fit for a prosthesis. In the example of knee joint arthroplasty, it is sometimes necessary to augment the inferior portion of the femoral component of the prosthesis to add additional thickness to the prosthesis to compensate for the lack of sufficient boney tissue.
Augmentation of the boney mass can be accomplished by securing augmenting devices to a component of the joint prosthesis, such as a femoral component. Some earlier devices used to augment knee femoral components must be cemented to the inferior surface of the femoral component. The techniques used to install such devices require accurate measurements and a great deal of precision since the augmenting device is difficult, if not impossible, to remove once it is secured to the prosthesis. These techniques also tend to be rather time consuming.
An improved augmentation device is described in U.S. Pat. No. 4,936,847 (Manginelli). This patent discloses an augmentation system that can be removeably and replaceably secured within a femoral component of a knee joint prosthesis. Such a design is advantageous because it avoids the need to cement augmenting devices to the inferior surface of the femoral component. As a result, augmenting devices of varying thicknesses can be fitted into place on the inferior surface of the femoral component. The augmenting devices can be removed and replaced with devices having different dimensions until the proper augmentation thickness is determined. Such an augmentation system, however, requires a specially constructed femoral component.
Despite existing augmentation systems, there remains a need to provide improved systems that allow standard augmenting components to be easily and securely affixed within a prosthesis component. The cost of joint prostheses that utilize many current augmentation systems can be quite high because the tight tolerances required often result in a high scrap rate. There is thus a need for an augmentation system that allows augmenting devices to be easily and securely fitted to prosthesis components.
It is thus an object of the invention to provide a prosthesis augmentation system that securely and easily fits within a component of a joint prosthesis. A further object is to provide an augmentation system that offers more cost effective manufacturing potential as well as a reduced part rejection rate. Another object is to provide an augmentation system that is well suited for use with femoral components of knee joint prostheses. It is also an object to provide an augmentation system that offers a great deal of versatility in that it can be used with different types of femoral components, including cruciate retaining and cruciate sacrificing femoral components. A further object is to provide an augmentation system that can be used in a prosthesis component without the need for post-casting modification of the prosthesis. Yet another object is to provide an augmentation system that can be easily installed without compromising prosthesis alignment. Other objects will be apparent to those of ordinary skill in the art upon reading the description that follows.